Influence of electrode-sensing material contact area on MWCNT-based gas sensor performance

Abstract

Multi-walled carbon nanotubes (MWCNTs) have emerged as promising sensing materials due to their advantages such as room-temperature operation, durability, large-area coating capability, and tunable electrical properties. While considerable research has focused on surface modification of CNTs, the influence of the contact area between the sensing material and the electrode has largely been overlooked. In this study, we systematically investigated the effect of contact area on the sensing performance of MWCNT-based ammonia gas sensors. Sensors with different contact areas were fabricated, and the resistance changes under ammonia gas exposure were measured. The results showed that the response characteristics increased sharply up to a contact area of 10 mm², followed by a gradual saturation trend. Analysis of the response rate per unit area revealed that the most efficient contact area was around 14 mm². This behavior can be attributed to the percolation threshold effect, which induces a steep resistance change at very small contact areas, and the dominance of parallel resistance behavior at larger areas, leading to a gradual decrease in slope.